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Abstract:

A device for reducing hydraulic-fluid oscillation in a hydraulic system,
in particular in a hydraulic system of an aircraft, wherein the hydraulic
system comprises a pump that is driven by a drive, which pump conveys a
fluid to a hydraulic line by pressure pulsation. The device comprises an
actuator, arranged in the hydraulic line for generating pressure
pulsation that compensates for the pressure pulsation of the pump.

Claims:

1. A device for reducing hydraulic-fluid oscillation in a hydraulic system
of an aircraft, wherein the hydraulic system comprises a pump, driven by
a drive, which pump conveys a fluid to a hydraulic line by pressure
pulsation, the device comprising an actuator, arranged in the hydraulic
line for generating pressure pulsation that compensates for the pressure
pulsation of the pump, wherein the actuator is controlled by a control
device as a function of the pressure pulsation occurring in the hydraulic
line, and a sensor in the hydraulic line for registering the occurring
pressure pulsation, which sensor provides a respective output signal to
the control device, wherein the sensor is arranged in the hydraulic line
so as to be upstream of the actuator.

2. The device of claim 1, wherein the sensor is arranged in the hydraulic
line so as to be in close proximity to the outlet of the pump.

3. The device of claim 1, wherein the control device controls the actuator
to minimise the pressure pulsation registered by the pressure sensor.

4. The device of claim 3, wherein the pressure sensor is arranged in the
hydraulic line at a distance of less than/equal to λ/6 from the
actuator, wherein λ is the characteristic wavelength of the
hydraulic-fluid oscillation in the hydraulic line to be reduced.1

5. The device of claim 1, wherein the pump is an axial piston pump.

6. The device of claim 1, wherein the actuator is driven electrically.

7. The device of claim 1, wherein the actuator is driven hydraulically or
pneumatically.

8. The device of claim 1, wherein the control device controls the actuator
to generate pressure pulsation according to frequency and amplitude such
that the total of the pressure pulsation of the pump and of the actuator
is kept to a minimum.

9. The device of claim 1, wherein the control device operates
electronically.

10. (canceled)

11. (canceled)

12. A method for reducing hydraulic-fluid oscillation in a hydraulic
system of an aircraft, comprising:providing a pump driven by a
drive;conveying a fluid by the pump to a hydraulic line by pressure
pulsation;generating pressure pulsation by an actuator arranged in the
hydraulic line that compensates for the pressure pulsation of the
pump;controlling the actuator as a function of the pressure pulsation
occurring in the hydraulic line by a controller;registering the occurring
pressure pulsation by a sensor in the hydraulic line; andproviding a
respective output signal to the controller;wherein the sensor is arranged
in the hydraulic line so as to be upstream of the actuator.

Description:

REFERENCE TO RELATED APPLICATIONS

[0001]This application claims the benefit of the filing date of German
patent application 10 2005 058 547.7, filed on Dec. 8, 2005, and of U.S.
Provisional Patent Application No. 60/780,553, filed Mar. 9, 2006, the
disclosures of which are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002]The invention relates to a device for reducing hydraulic-fluid
oscillation in a hydraulic system, in particular in a hydraulic system of
an aircraft, according to the precharacterising part of claim 1.

[0003]Hydraulic systems are used in a wide range of applications for
conveying fluids that are used for a host of different purposes and may
be conveyed at greatly different pressures. The fluids conveyed at
pressure may perform mechanical work for control purposes or motive power
purposes; they may be used as fuels or oxidising agents; they may be
lubricants or other materials, any fluids, as used in motive power
engineering, materials processing etc.

[0004]In aircraft, typically, several hydraulic systems that are usually
independent are provided, which hydraulic systems by pumps, in particular
axial piston pumps, generate the necessary pressure in the systems. In
this arrangement pressure pulsation in the hydraulic lines occurs, which
pulsation is acoustically perceived as disagreeable noise, and, because
such pulsation subjects the lines to additional loads, it may also
increase the possibility of leakages occurring. The undesirable side
effects associated with such pressure pulsation occur in particular also
in the case of pumps of aircraft engines.

[0005]According to the state of the art, pressure pulsation of the type
mentioned may be reduced by reverberation attenuators, which however on
the one hand have to be installed in close proximity to the pumps, and on
the other hand, in particular in the case of engine pumps that operate at
relatively low frequencies, have to be quite voluminous, which means that
because of the lack of space they cannot be accommodated in the engine
pylon in close proximity to the pumps.

[0006]From DE 103 16 946 A1 a device for attenuating pressure oscillation
in a hydraulic line is known, in which device an actuator for generating
pressure oscillation in the hydraulic line is arranged between a pressure
source in the form of a pump and a consumer. By a control-/regulating
device the actuator is to be controlled such that it generates pressure
oscillation that is at least approximately in phase opposition to the
pressure oscillation detected by a sensor in the hydraulic line. In this
known device the actuator that generates the pressure oscillation that is
in phase opposition is arranged in the hydraulic line at a smaller
distance from the pump, i.e. upstream of the sensor that generates the
pressure oscillation.

[0007]Furthermore, from the publication "The Vibration Active Control on
the Fluid Borne Noise", Jiao Zongxia, Chen Ping, Hua Quing, Wang
Shaoping, College of Automation Science and Electrical Engineering,
Beijing University of Aeronautics and Astronautics, a device for actively
reducing hydraulic fluid oscillation in a hydraulic system is known. This
hydraulic system comprises a pump that is provided for conveying the
hydraulic fluid in a connected hydraulic fluid line system, and further
comprises a first relief valve that is connected to the hydraulic line
system. A second relief valve that is furthermore connected to the
hydraulic line system is a piezoelectrically operable actively
controllable valve that is provided for reducing the hydraulic-fluid
oscillation in the hydraulic system. Said valve is actuated by fast
Fourier transforms (FFT) carried out in a computer in response to the
pressure oscillation registered on the hydraulic system. The hydraulic
fluid that is led away by way of the actively controllable valve is
collected as a leakage quantity and is returned to the hydraulic system.
In addition to the useable feed quantity, the feed pump of this known
hydraulic system thus also has to convey the quantity of hydraulic fluid
that has been led away by way of the actively controllable valve and that
has been collected as a leakage quantity.

[0008]Finally, from the Japanese patent abstract 05180390 a device for
attenuating noise-generating oscillation in a line is known, in which
device a first oscillation sensor is provided near a pump that is
considered to be the primary oscillation source, which oscillation sensor
is installed on the outside of the line and contains an oscillation
acceleration detector, and, at a predetermined distance from said first
oscillation sensor, an electromagnetic excitation device that is referred
to as the secondary oscillation source is provided on the line. Again at
a predetermined space from the electromagnetic excitation device, a
second oscillation sensor, which also comprises an oscillation
acceleration detector, is provided as a fault sensor. The first
oscillation sensor, the fault sensor, and the electromagnetic excitation
device are electrically connected to a filter circuit that serves as a
regulating device so as to reduce the noise in the line, which noise has
been generated by the oscillation.

SUMMARY OF THE INVENTION

[0009]It is an object of the invention to create a device for reducing
hydraulic-fluid oscillation, which device is effective and requires
little space.

[0010]This object is solved by a device for reducing hydraulic-fluid
oscillation, having the features of claim 1. Advantageous embodiments and
improvements of the device according to the invention are stated in the
dependent claims.

[0011]According to an exemplary embodiment of the invention a device is
provided for reducing hydraulic-fluid oscillation in a hydraulic system,
in particular in a hydraulic system of an aircraft, wherein the hydraulic
system comprises a pump, driven by a drive, which pump conveys a fluid to
a hydraulic line by pressure pulsation, and further comprises an
actuator, arranged in the hydraulic line, which actuator is provided for
generating pressure pulsation that compensates for the pressure pulsation
of the pump, wherein the actuator is controlled by a control device as a
function of the pressure pulsation occurring in the hydraulic line, and
in the hydraulic line a pressure- or oscillation sensor for registering
the occurring pressure pulsation is provided, which pressure- or
oscillation sensor provides a respective output signal to the control
device. According to the invention, the pressure sensor is arranged in
the hydraulic line so as to be upstream of the actuator.

[0012]The terms "hydraulic system" or "hydraulic line" etc. used in this
document are to be interpreted in their widest sense; they refer to any
fluid that conforms to the laws of hydraulics, i.e. apart from so-called
hydraulic fluid or hydraulic oil they also refer to fuels, lubricants,
oxidising agents and any other fluids as used in motive power
engineering, materials processing etc.

[0013]According to an exemplary embodiment of the invention the components
that have to be arranged in close proximity to the pump are very small so
that the space requirements both in the case of retrofitting and in the
case of new constructions are very modest. This is advantageous in
particular in the case of engine pumps of aircraft. According to an
exemplary embodiment of the invention apart from noise, mechanical loads
acting on the hydraulic system, which mechanical loads result from
pressure pulsation, are also reduced.

[0014]According to an exemplary embodiment of the invention, the pressure
sensor is arranged in the hydraulic line so as to be in close proximity
to the outlet of the pump.

[0015]According to an exemplary embodiment, the control device controls
the actuator with a view to minimising the pressure pulsation registered
by the pressure sensor.

[0016]According to an exemplary embodiment of the invention, the pressure
sensor is arranged in the hydraulic line at a distance of less than/equal
to λ/6 (λ=characteristic wavelength of the hydraulic-fluid
oscillation in the hydraulic line, which hydraulic-fluid oscillation is
to be reduced) from the actuator.

[0017]According to an exemplary embodiment of the invention the pump may
be an axial piston pump.

[0018]According to an exemplary embodiment of the invention the actuator
may be driven electrically.

[0019]According to an exemplary embodiment of the invention the actuator
may be driven hydraulically or pneumatically.

[0020]According to an exemplary embodiment of the invention, it is
provided for the control device to control the actuator with a view to
generating pressure pulsation according to frequency and amplitude such
that the total of the pressure pulsation of the pump and of the actuator
is kept to a minimum.

[0021]According to an exemplary embodiment, the control device operates
electronically.

[0022]According to an exemplary use, the device is provided for reducing
hydraulic-fluid noise in engine pumps of an aircraft engine, which engine
pumps operate at low frequencies.

[0023]In this use the device may advantageously be arranged in the engine
pylon.

DETAILED DESCRIPTION OF THE FIGURE

[0024]Below, an exemplary embodiment of the invention is explained with
reference to the drawing.

[0025]The FIGURE shows a diagrammatic view of a device for reducing
hydraulic-fluid oscillation, in particular hydraulic-fluid noise in a
hydraulic system, in particular in a hydraulic system of an aircraft,
according to an exemplary embodiment of the invention.

[0026]The device shown in the FIGURE is used for reducing hydraulic-fluid
oscillation, in particular hydraulic-fluid noise in a hydraulic system,
such as a hydraulic system of an engine (not shown) of an aircraft.

[0027]The hydraulic system comprises a pump 2, which is driven by a drive
1 in the form of a motor, typically an axial piston pump that operates at
relatively low frequencies. By way of pressure pulsation this pump
conveys a fluid (fuel) to the engine by way of a hydraulic line 3.

[0028]Arranged in the hydraulic line 3 is an electrically driven actuator
5, which in turn is provided for generating pressure pulsation that is to
compensate for the pressure pulsation of the pump 2. The actuator 5 is
controlled by an electronically operating analog or digital control
device 4 as a function of pressure pulsation that occurs in the hydraulic
line 3. The pressure pulsation that occurs in the hydraulic line 3 is
registered by a pressure- or oscillation sensor 6 that transmits a
corresponding output signal to the control device 4.

[0029]The control device 4 controls the actuator 5 with a view to
generating pressure pulsation according to frequency and amplitude such
that the total of the pressure pulsation of the pump 2 and the actuator 5
is kept to a minimum, in other words so that the pressure pulsation
registered by the pressure sensor 6 is minimal.

[0030]The actuator 5 may be driven by way of a single harmonic frequency
or by way of a fundamental oscillation that is superposed by harmonic
oscillation, depending on the type of pressure pulsation generated by the
pump 2.

[0031]Driving the actuator 5 in response to the output signal generated by
the pressure sensor 6 may take place in the manner of forward control, in
which the pressure pulsation generated by the actuator 5 is generated
according to a predetermined function of the pressure pulsation measured
by the pressure sensor, or in the manner of regulation, in which, as
described above, the pressure pulsation registered by the pressure sensor
6 becomes minimal.

[0032]In the exemplary embodiment shown, the pressure sensor 6 is arranged
in the hydraulic line 3 so that it is situated upstream of the actuator 5
and in close proximity to the outlet of the pump 2, while the pressure
sensor 6 is arranged in the hydraulic line 3 at a distance of less
than/equal to λ/6 (λ=characteristic wavelength of the
hydraulic-fluid oscillation in the hydraulic line, which hydraulic-fluid
oscillation is to be reduced) from the actuator 5, so as to prevent the
occurrence of longitudinal resonance in the hydraulic line in the
frequency range that is of interest.

[0033]The device can, in particular, be arranged in the engine pylon of an
aircraft.

[0034]It should be noted that the term `comprising` does not exclude other
elements or steps and the `a` or `an` does exclude a plurality. Also
elements described in association with different embodiments may be
combined.

[0035]It should be noted that the reference signs in the claims shall not
be construed as limiting the scope of the claims.